The ability to recognise women who are at-risk of preterm labour is often difficult. Over 50% of women who are identified with factors associated with an increased risk of preterm birth will ultimately deliver at term. The cervicovaginal fluid (CVF) comprises of a range of proteins secreted by gestational tissues, making it an ideal candidate for the screening of differentially expressed proteins associated with preterm labour. CVF samples were collected from at-risk asymptomatic women. Two-dimensional gel electrophoresis techniques were used to examine the CVF proteome of women who spontaneously delivered preterm 11-22 days later, compared to gestation-matched women who delivered at term. Five candidate biomarkers were selected for further validation in a larger independent cohort of asymptomatic women. Thioredoxin (TXN) and interleukin-1 receptor antagonist (IL1RN) expression in the CVF were found to be significantly reduced up to 90 days prior to spontaneous preterm labour compared to women who subsequently delivered at term. TXN was able to predict spontaneous preterm labour within 28 days after sampling with high positive and negative predictive values of 75.0% and 96.4%, respectively. IL1RN also showed comparable positive and negative predictive values of 72.7% and 95.7%, respectively. The discovery of these differentially expressed proteins may assist in the development of a new predictive bedside test in identifying asymptomatic women who have an increased risk of spontaneous preterm labour.